Magnetic Properties of the Ferromagnetic Shape Memory Alloys Ni 50+ x Mn 27- x Ga 23 in Magnetic Fields.

Thermal strain, permeability, and magnetization measurements of the ferromagnetic shape memory alloys Ni _{50+ x} Mn _{27- x} Ga ₂₃ ( x = 2.0, 2.5, 2.7) were performed. For x = 2.7, in which the martensite transition and the ferromagnetic transition occur at the same temperature, the martensite transition starting temperature T _Ms shift in magnetic fields around a zero magnetic field was estimated to be d T _Ms /d B = 1.1 ± 0.2 K/T, thus indicating that magnetic fields influences martensite transition. We discussed the itinerant electron magnetism of x = 2.0 and 2.5. As for x = 2.5, the M ⁴ vs. B/M plot crosses the origin of the coordinate axis at the Curie temperature, and the plot indicates a good linear relation behavior around the Curie temperature. The result is in agreement with the theory by Takahashi, concerning itinerant electron ferromagnets.